1. Field of the Invention
This invention relates to a resilient electrical contact assembly for connecting to a bus bar a conductor having a relatively large diameter, characterized by the provision of an auxiliary electrically-conducting contact for improving the conductivity between the conductor and the bus bar.
2. Brief Description of the Prior Art
Resilient electrical contacts for connecting a conductor to a bus bar are well known in the prior art. Such contacts normally are compression springs having a generally d-shaped configuration and include a clamping leg containing an opening for receiving the bus bar and the conductor in lateral side-by-side relation, and a contact leg which resiliently biases the bus bar and the conductor together against a clamping edge of the opening. Such compression spring connections are employed on a large scale in terminal blocks. If the terminal blocks are designed as peak current terminals and if accordingly one must connect conductors with large conductor cross-sections, then the by no means inconsiderable bending strength of such conductors in combination with intensive conductor movements during the wiring work can lead to such a severe mechanical stress of the clamping point that its electrical contact safety will also be endangered.
To improve contact safety, it has become known in the area of the clamping point in the case of compression spring connections, one can make a contact chamber having walls that the conductor can contact.
Such a spring connection is disclosed in German patent No. DE 197 41 135 A1; here, the contact chamber is made on the bus bar itself by multiple angle bends of wall segments. This extraordinarily complicates the production of the bus bar. The attendant high productions costs are particularly negative with a view to the mass and series part character of such a part. In this German patent, a compression spring connection of the kind involved is provided, and in order to form the contact chamber, one uses an accessory part in the form of a strap with a U-shaped cross-section, which is firmly connected with an upward-bent terminal piece of the bus bar piece and which, after its fastening together with the corresponding surface of the bus bar piece, forms an all-around enclosed contact chamber.
To be sure, this does not complicate the production of the bus bar piece; nevertheless, the strap-shaped accessory piece must be fastened in a rather expensive manner in terms of production engineering by means of calking, riveting, soldering, or welding upon the bus bar piece. The basic structure of the accessory part must also be relatively complicated to offer the possibility of attachment upon the bus bar piece. This means that here again, one must accept high production costs.
The present invention was developed to provide a resilient contact assembly of the kind involved which, while guaranteeing sufficient contact safety, can be made in a particularly simple and thus reasonable priced fashion.
Accordingly, a primary object of the present invention is to provide a resilient contact assembly including a separate, loosely-assembled, electrically conductive auxiliary contact that improves the electrical conductivity between a bus bar and an oversize conductor having a relatively large diameter.
According to a more specific object of the invention, the auxiliary contact is a loose insertion part which, when in the inserted state, is retained mechanically by the clamping side of the resilient contact and which is retained upon the bus bar piece in an electrically contacting fashion. In this way, there is no need for any structural changes on currently available bus bar pieces.
According to a further object of the invention, the auxiliary contact is provided with a body portion that is in contiguous electrical engagement with the bus bar, and at least one additional portion that cooperates with the body portion to define a chamber for receiving the bare end portion of the oversized conductor, thereby to provide means for engaging additional surface areas of the conductor and thus increase the conductivity between the conductor and the bus bar. Moreover, one can also dispense with the additional fastening of an accessory part on the bus bar piece because the loose insertion part forming the contact chamber is now retained on the bus bar piece by using the clamping force of the clamping side of the resilient contact.
The practical design of the insertion part features a contact side and a clamping side with which it is retained mechanically and in an electrically contacting manner by the clamping force of the clamping side of the resilient contact upon the bus bar piece, as well as corresponding to the particular design, one or two additional conductor contact surfaces. Thus, the insertion part itself has a simple structural design which contributes to simplified production of such a resilient contact connection.
In this design, at least one side of the contact chamber, formed by the insertion part, remains open. Such resilient contact connections are used in terminal blocks and are thus in the latter""s insulation material housings; therefore, the open side can advantageously be closed off by the insulation material, assuming the terminal block housing has been properly designed.
In accordance with another object of the invention, the body portion of the auxiliary contact includes a bent positioning portion that conforms with a corresponding bent portion on the bus bar, thereby to position the auxiliary contact relative to the bus bar.